A write head is typically combined with a magnetoresistive (MR) read head to form a merged MR head, certain elements of which are exposed at an air bearing surface (ABS). The write head comprises first and second pole pieces connected at a back gap that is recessed from the ABS. The first and second pole pieces have first and second pole tips, respectively, which terminate at the ABS. An insulation stack, which comprises a plurality of insulation layers, is sandwiched between the first and second pole pieces, and a coil layer is embedded in the insulation stack. A processing circuit is connected to the coil layer for conducting write current through the coil layer which, in turn, induces write fields in the first and second pole pieces. A non-magnetic gap layer is sandwiched between the first and second pole tips. Write fields of the first and second pole tips at the ABS fringe across the gap layer. In a magnetic disk drive, a magnetic disk is rotated adjacent to, and a short distance (fly height) from, the ABS so that the write fields magnetize the disk along circular tracks. The written circular tracks then contain information in the form of magnetized segments with fields detectable by the MR read head.
An MR read head includes an MR sensor sandwiched between first and second non-magnetic gap layers, and located at the ABS. The first and second gap layers and the MR sensor are sandwiched between first and second shield layers. In a merged MR head, the second shield layer and the first pole piece are a common layer. The MR sensor detects magnetic fields from the circular tracks of the rotating disk by a change in resistance that corresponds to the strength of the fields. A sense current is conducted through the MR sensor, where changes in resistance cause voltage changes that are received by the processing circuitry as readback signals.
One or more merged MR heads may be employed in a magnetic disk drive for reading and writing information on circular tracks of a rotating disk. A merged MR head is mounted on a slider that is carried on a suspension. The suspension is mounted to an actuator which rotates the magnetic head to locations corresponding to desired tracks. As the disk rotates, an air layer (an “air bearing”) is generated between the rotating disk and an air bearing surface (ABS) of the slider. A force of the air bearing against the air bearing surface is opposed by an opposite loading force of the suspension, causing the magnetic head to be suspended a slight distance (flying height) from the surface of the disk. Flying heights are typically on the order of about 0.02 μm.
One on-going objective in the industry is to improve or increase the amount of data that can be stored on a disk, and to design magnetic heads which can adequately read from and write data to these disks. One promising technique to increase the disk storage capacity is heat-assisted magnetic recording (HAMR), which may also be referred to as optically-assisted magnetic recording or thermally-assisted magnetic recording. This technique utilizes a recording medium that has a higher coercivity than current media so that it has more resistance to thermal instability at normal operating temperatures. Therefore, more data can be adequately stored on the media. Unfortunately, a higher coercivity means that the platter tends to resist reacting to magnetic fields at typical operating temperatures. Therefore, it is difficult to write data to such media. To sufficiently write data to high coercivity media, a disk drive needs to heat a writable portion of the disk to lower its coercivity as the write head writes data thereto.
Both HAMR and magneto-optical (MO) disk drives can utilize lasers to the heat a portion of the recording media in order to lower its coercivity. When reading data, however, HAMR drives read directly from the disk using a conventional GMR head. On the other hand, MO drives bounce light off the disk and read bits from changes in the laser beam with an optical sensor. The downside of using a laser for heating is the finite spot size of the laser spot. This spot is typically at the diffraction limit of the light. In addition, the wavelength of the light is not easily scalable to shorter wavelengths to achieve smaller heated areas of the disk.
Accordingly, what is needed is a magnetic head which provides for an increased amount of data to be stored on a disk, as well as improvements and alternatives to the prior art.